Wireless or mobile communication networks (also referred to as cellular networks) in which a User Equipment (UE) (such as a mobile handset) communicates via a radio link to a network of base stations (e.g., eNBs) or other wireless access points connected to a telecommunications network, have undergone rapid development through a number of generations. The initial deployment of systems using analog signaling has been superseded by second Generation (2G) digital systems such as Global System for Mobile communications (GSM), which typically use a radio access technology known as GSM Enhanced Data rates for GSM Evolution Radio Access (GERA), combined with an improved core network.
Second generation systems have themselves been replaced by or augmented by third Generation (3G) digital systems such as the Universal Mobile Telecommunications System (UMTS), which uses a Universal Terrestrial Radio Access Network (UTRAN) radio access technology and a similar core network to GSM. UMTS is specified in standards produced by the 3rd Generation Partnership Project (3GPP). Third generation standards provide for a greater throughput of data than is provided by second generation systems. This trend is continued with the move towards fourth Generation (4G) systems.
The 3GPP designs, specifies and standardizes technologies for mobile (cellular) wireless communications networks. Specifically the 3GPP produces a series of Technical Reports (TR) and Technical Specifications (TS) that define 3GPP technologies. The focus of the 3GPP is currently the specification of standards beyond 3G, and in particular an Evolved Packet System (EPS) offering enhancements over 3G networks, including higher data rates. The set of specifications for the EPS comprises two work items: Systems Architecture Evolution (SAE, concerning the core network) and Long Term Evolution (LTE) concerning the air interface. The first set of EPS specifications were released as 3GPP Release 8 in December 2008. LTE uses an improved radio access technology known as Evolved-UTRAN (E-UTRAN), which offers potentially greater capacity and additional features compared with previous standards. SAE provides an improved core network technology referred to as the Evolved Packet Core (EPC), and in particular provides access to the Internet or proprietary networks. Despite LTE strictly referring only to the air interface, LTE is commonly used to refer to the whole of the EPS, including by 3GPP themselves. LTE is used in this sense in the remainder of this specification, including when referring to LTE enhancements, such as LTE Advanced. LTE is an evolution of the UMTS and shares certain high level components and protocols with UMTS. LTE Advanced offers still higher data rates compared to LTE and is defined by 3GPP standards starting with Release 10. LTE Advanced is considered to be a 4G mobile communication system by the International Telecommunication Union (ITU). It will be appreciated, however, that the present disclosure is not limited to 3GPP networks, and is specifically not limited to LTE networks. The skilled person will appreciate that the present disclosure could be applicable to interworking between any cellular network and another network.
Wireless Local Area Networks (WLANs) operate to connect two or more devices through a wireless bearer. There are many commercially deployed WLANs providing a connection through an Access Point (AP) to the Internet or a proprietary network. The majority of commercially deployed WLANs are compliant with Institute of Electrical and Electronic Engineers (IEEE) 802.11 standards, also referred to as Wi-Fi. It will be appreciated, however, that the present disclosure is not limited to Wi-Fi networks. WLANs were originally primarily used to provide wireless access to the data networks for laptops and other portable computing devices. More recently, it has become common for mobile terminals designed to operate in cellular networks to also be able to access WLANs. This provides advantages by allowing users access to higher data rates afforded by WLANs, and often lower pricing by network operators, when downloading large volumes of data.
FIG. 1 schematically illustrates a system architecture suitable for interworking between a 3GPP compliant network and a WLAN network according to the related art.
Referring to FIG. 1, an overview of a network architecture for interworking between an LTE network and a WLAN of the related art is provided. It will be appreciated that FIG. 1 is a simplification and a typical implementation of LTE will include further components. The LTE system comprises three high level components: at least one UE 102, the E-UTRAN 104 and the EPC 106. The EPC 106 communicates with Packet Data Networks (PDNs) 108 outside of the LTE network identified in FIG. 1 as being the Internet. FIG. 1 shows certain of the key component parts of the EPC 106. In FIG. 1, interfaces between different parts of the LTE system are shown by lines connecting the components. The double ended arrow labelled LTE indicates the air interface between the UE 102 and the E-UTRAN 104.
The E-UTRAN 104 comprises a single type of component: an eNB which is responsible for handling radio communications between the UE 102 and the EPC 106 across the air interface. An eNB controls UEs 102 in one or more cell, and so LTE may be considered to be a cellular network in which the eNBs provide coverage over one or more cells. Typically, there is a plurality of eNBs within an LTE system.
Key components of the EPC 106 are shown in FIG. 1. It will be appreciated that in an LTE network there may be more than one of each component according to the number of UEs 102, the geographical area of the network and the volume of data to be transported across the network. Data traffic is passed between each eNB and a corresponding Serving Gateway (S-GW) 110 which routes data between the eNB and a PDN Gateway (P-GW) 112. The P-GW 112 is responsible for connecting a UE to one or more PDNs in the outside world, referred to in FIG. 1 simply as the Internet 108. A Mobility Management Entity (MME) 114 controls the high-level operation of the UE 102 through signaling messages exchanged with the UE 102 through the E-UTRAN 104. Each UE is registered with a single MME. There is no direct signaling pathway between the MME 114 and the UE 102 (communication with the UE 102 being across the air interface via the E-UTRAN 104). Signaling messages between the MME 114 and the UE 102 comprise EPS Session Management (ESM) protocol messages controlling the flow of data from the UE to outside networks and EPS Mobility Management (EMM) protocol messages controlling the rerouting of signaling and data flows when the UE 102 moves between eNBs within the E-UTRAN. The MME 114 exchanges signaling traffic with the S-GW 110 to assist with routing data traffic.
The EPC 106 also includes an Access Network Discovery and Selection Function (ANDSF) server 116. The ANDSF server 116 serves to assist UEs to discover non-3GPP networks, including WLANs such as Wi-Fi or Worldwide Interoperability for Microwave Access (WIMAX). The operation of an ANDSF server is defined in 3GPP TS 23.402 V11.5.0: Architecture enhancements for non-3GPP accesses. The ANDSF server 116 also provides the UE with rules or policies for accessing non-3GPP networks, as mandated by network operators. An ANDSF server 116 may be configured to enable Inter-System Mobility Policy (ISMP) or Inter-System Routing Policy (ISRP). Under ISMP a UE may only have one active access network connection (for example, LTE or Wi-Fi) at any one time. Under ISRP a UE may have more than one active access network connection (for example, both LTE and Wi-Fi) at any one time. Under ISRP a UE may employ IP Flow Mobility (IFOM), Multiple-Access PDN Connectivity (MAPCON) or non-seamless Wi-Fi offload according to operator policy and user preferences. The ANDSF server 116 also provides discovery information, specifically a list of networks that may be available in the vicinity of the UE and information assisting the UE to expedite the connection to these networks.
FIG. 1 also shows a WLAN comprising an AP 118 which provides a connection to a PDN, referred to in FIG. 1 as the AP 118 being connected to the Internet 108. The air interface between the UE 102 and the AP 118 is identified by the double ended arrow labelled Wi-Fi. For interworking between 3GPP networks and WLANs it is desirable that the interworking operates irrespective of whether there is any direct interface between the 3GPP network and the WLAN.
Offloading data traffic to a WLAN is desirable for both the operator and the subscriber as noted above for reasons of improved data rates and reduced demand on 3GPP networks. However, if handled inappropriately the result may a reduction in performance, for instance if a UE offloads data traffic to an already overloaded WLAN. It is known to base network selection decisions on WLAN and 3GPP signal strength without taking into account the current network load. However, the WLAN signal strength may be unrelated to the WLAN network load. Alternatively, a UE may not connect to a WLAN due to relatively low WLAN signal strength despite overloading on the 3GPP network. The result is inefficient usage of the total capacity of a combined 3GPP network and WLAN.
Further problems occur for some UEs which disable 3GPP data access when connected to a WLAN. Furthermore, users frequently disable WLAN connectivity to preserve battery life (which is reduced by scanning for available WLANs). Reduced battery life may be partially mitigated by the network providing information about locally available WLAN access points though this does increase 3GPP network traffic.
System interworking between WLAN and 3GPP has been available since 3GPP Release-6 and is defined in TS 23.234 “3GPP system to Wireless Local Area Network (WLAN)”. TS 23.234 defined loose coupling between the UMTS Core Network (CN) and WLAN networks including common SIM-based authentication mechanisms and access to operator services via a Packet Data Gateway (PDG). This was further enhanced in TS 23.327 “Mobility between 3GPP-Wireless Local Area Network (WLAN) interworking and 3GPP systems” in 3GPP Release-8, which defined seamless mobility between the two networks based on DSMIPv6.
WLAN Interworking with the EPC is defined in TS 23.402 “Architecture enhancements for non-3GPP accesses”. The simplest interworking option supported by EPC is non-seamless WLAN offload, in which case the UE connects to WLAN access network when it is available in parallel with 3G/LTE connection. UE data traffic is not routed through the operator's core network and there is no service continuity when the UE moves out of WLAN coverage.
Seamless mobility in which an IP address is preserved during offloading ensures that there is no service interruption when the UE moves between the LTE network and a WLAN. WLAN interworking has been enhanced since Release-10 to support simultaneous connections to 3GPP networks and WLANs. For instance, the UE may connect to a 3GPP operator's services via the 3GPP network and to the Internet via WLAN.
However, a reduction in user experience may occur during cellular network and WLAN interworking if a large number of UEs switch networks. Accordingly, there is a need to provide mechanisms for controlling the offloading of data flows between cellular networks and WLANs that balances network load requirements for both networks, provides proper means for controlling the amount of traffic that is offloaded, and minimizes the risk of small changes in load for one or other network resulting in unintended switching of many data flows.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.